Electrometallurgical process for extracting copper from its ores.



' To all whomit may concern:

LUCIEN JUMAU, OF PARIS, FRANCE.

ELEGTROMETALLURGICAL rRocEss FOR EXTRACTING COPPER FROM m was;

Specification of Letters Patent.

Patented. Sept. 24, 1907.

Application med December 29,1905. Serial rmaasze.

Be it known that 1, LUoIEN JUMAU, a citizen of France, residing at Paris, in the said Reynblic, have invented new and useful Improvements in Processes Electrometallulgical for Extracting v Copper from Its Ores, (for which a French patent has been filed N- vembcr 29, 1905,) of which the following is a specification.

This invention relates to an electro-metallurgical process for extracting copper from its ores, whereby a product. is obtained of greater purity than that obtained by analogous processes now in use, while. the

- working is more economical both in cost of electricity and in cost of reagents.

The invention also includes certain improvements in the construction of electrolytic vats wherein the process is to be coirducted- The process comprises the following successive operationsi Preparation of (m mnmom'acal solution of the copper contained in t71 e.0re.lor this purpose the ore, previously rotated or not, according to its nature, is leached with a solution of ammonia preferably mixed with an ammonia'cal salt to increase the solubility of the C01 once of, free ammonia is particularly suitable. The

leaching dissolves all the copper from the ore, and, in most cases, the copper only, which is especially advantageous, since when the solution is electrolyzed pure copper is deposited and the paths are not dirtiod as in the processes at present in use. The ammoniacal solution of copper thus obtained may be electrolyzed directly if the qualities of copper electrolytically deposited from an ammoniacal solution are suitable for the purpose to which the metal is to be put. Or the solution may be first treated by either of the. two fol: lowing methods. The ammonia whcrewith the ore was treated may be recovered by evaporation and again used in a subsequent lixiviation of the ore. During the evapm'ation .of the ammonia the copper is precipitated as oxid and may be again dissolved, for instance in an acidsuch as sulfuric acid or in ammonia; there is thus obtained a solution which contains only copper. The cupric salts contained in the ammoniacal solution obtained by leaching the ores or by re-dissolving the copper precipitated by evaporating the original solution, may be convertedinto cuprous salts, a proceeding particularly applicable when sulfite ores are under treatment; the reduction may be effected by passing a current of sulfur dioxid into thelammoniacal solution, whereby cuprous sulfite, or. cuproso-cupric sulfite, or a double sulfite of copper andammonia is formed, these salts being able to co-exist in the solution treated with sulfur dioxid, in proportions varying according to the duration of tlre treatment. The solution thus treated maybe electrolyzed in a neutral, acid or basic condition.

effects an important economy in electricity; for whereas 1 ampere-hour deposits 1.186 grams of copper from a eupric salt, it deposits 2.372 grains from a cuprous salt under like conditions.

The sulfur dioxid necessary for the reduction need cost nothing when sulfid ores are being dealt with, as it is produced by the preliminary roasting of the ore; in other cases the cost of the sulfur dioxid is largely compensated .b the economy in electricity.

When the ammoniacal solution containing the copper of the ore has been treated in the manner described, it is electrolyzed. This operation in actual practice is distinguished by being conducted in presence of a depolarizing agent whereby the potential at the anode is kept sufficiently low to avoid liberation of oxygen or the formation of peroxid of lead when the anode is of lead. This depolarizer is the ammoniacal cuprous solution itself, when the aforesaid reduction with sulfur dioxid has been carried out, or it may be a solution of ammonium sulfite which is basic, neutral or acid. It is obvious that oxygen will not be liberated at the anode so long as the sulfites in the solution an electrolysis with a minimum cost for electricity and with production of pure copper at the cathode.

After the electrolysis" the ammonia is recovered with an alkaline earth, preferably lime for cheapness sake, to liberate the ammonia. It may be remarked that, in most cases, the small cost involved in this treatment with lime may be eliminated; for the majority of copper ores contain a'certain proportion of lime, magnesia or baryta, generally as carbonate, so .thatthe ore itself, whether roasted or not, maybe substituted for lime in recovering the ammonia.

there is used an electrolytic vat which may or may not have a diaphragm and wherein the liquid and the phragm, it mayconsist of a porous material, not liable to be attacked by the electrolyte, and impregnated with gelatinous silica such as asbestos used, for example, in -the form of blue asbestos cloth which has been impregnated withgelatinous silica by immersion in a mixture of sulfuric acid and silicate'of soda; sucha diaphragm is very effective and has a low resistance to the passage of the electric current.

cylinder or the like, of copper orof any other metal or capable of resisting the electrolyte, such as lead or carbon, preferably in a. graphitic condition.

are not oxidized. The invention therefore, secures from the solution now free from copper, by mixing it For the process which has now been described,

The cathode is, of course, athin sheet, a plate, a.

The reduction of the eupric salts to cuprous salts electrodes may or may not move If there is a diasuitable conducting material; the anode is a metal of the ore in an ammonialcal solution b\' leachin" said ore 5 s with a. solution of ammonia mixed with an aninioniacal.

salt, reducing to cuprous salts. the cupric salts inthe said ammoniacal solution, by passing a current of sulfur ft'iboxid into said solution. and electrolyzing the reduced solution, said reduced solution acting meanwhile as a depolarizer at the anode. substantially as described.

2. The herein described process for extracting copper from its ores} which consistv ill tiifiStiiYillg the copper of theorem an ammoniacal solution by leaching said ore with a solution of ammonia mixed with an ammoniacal salt, reducing to'cnprous salts. the cnprie salts in the said ammoniacal solution, by passing a current of sulfur dioxid into. said, solution, electrolyzine' said reduced solution whi'clracts as a depolarizcr at the anode, and recovering the ammonia contained in the solution after the electrolysis by treating such solution with an alkalinca-arth, sub stantially as described.

3. The herein described process for extracting copper from its sultid ores, which consi ts in roasting said ores to drive of? sulfur dioxid and reduce the ores to an oxid.

collecting the sulfur dioxid evolved. leaching said oxid aavgoea with an ammoniacal solution consisting of a solution oi ammonia mixed with an aminoniacal salt, 1 stop: said collected sult'ur dioxid through said ammoniacal solution for reducing the cupric salts to cuprous salts. clectrolyzinc; said reduced solution which acts as a dcpolarlzer at the anode, and recovering the ammonia contained in the solution after electrolysis by treating, said solution with the hydrate 01' an alkaline earth metal.

-L The herein described process for extracting copper from its sultid ores, which consists in roasting said ores to-drive ol'f sulfur dioxid and reduce the ores to an oxid, collecting the sulfur dioxid evolved, leaching said oxid with an annnoni cal solution consiting of a solution of ammonia mixed with an ammonium sulfite, passing said collected sulfur dioxid through said ammoniacal solution for reducing the cupric salts to cuprous salts. elm 'ulyzing said reduced solution which acts as a depolarizcr at the anode, and recovering the ammonia contained in the solution after electrolysis by treating aid solution with milk of lime.

In witness whereof I have hereunto set the presence of two witnesses. 

